The neuropathology of autism: A systematic review of post-mortem studies of autism and related disorders

•Autism and related disorders display an overlap in presentation and neuropathology.•Impaired synaptic, metabolic, proliferation, apoptosis and immune pathways are repeatedly implicated.•Dysregulated non-coding RNAs and aberrant epigenetic profiles are consistently reported.•Strong evidence for GABAergic, glutamatergic and glial dysfunction is provided.•The cerebellum and frontal cortex are most consistently implicated.